The Cooperative Clinical Study of Dietary Modification on the Course of Progressive Renal Disease is a multi-institutional randomized clinical trial designed to assess the following two hypotheses: (1) Restriction of dietary protein reduces the rate of progression of chronic renal disease in humans. (2) Dietary protein restriction is nutritionally safe (if effective) in patients with progressive renal failure. This trial will be accomplished in four stages over a five and one-half year period--a 6-month protocol development stage, a 12-month pilot stage, a 3-year full-scale operation, and a 1-year analysis stage. It is anticipated that approximately 300 patients will be enrolled into the clinical trial from approximately 10 clinical centers. The following proposal describes the program, facilities, personnel and administrative structure of the Data Coordinating Center and Nutritional Coordinating Center for the multicenter clinical trial. The program of the Data Coordinating Center and Nutritional Coordinating Center will include participation in the development of the study protocol and of the detailed manual of operations during the planning phase of the study; the development, in cooperation with the clinics and the NIADDK program office, of appropriate data processing procedures and procedures for randomization. A major activity of the Data Coordinating Center and the Nutritional Coordinating Center will be the development of procedures for control of the quality of the study data. In addition to specific procedures for quality control, frequent visits by the Center's members to the participating clinics will be made to establish the close rapport and liaison necessary for the successful completion of a long-term effort such as this one. A comprehensive program of data management for the study will be undertaken by the Center's staff. This program will include data review and editing, data reduction, display and analysis, and generation of reports and publications.